using System;

namespace NetSpell.SpellChecker.Dictionary.Affix
{
	/// <summary>
	/// Summary description for AffixUtility.
	/// </summary>
	public sealed class AffixUtility
	{
		/// <summary>
		///     Initializes a new instance of the class
		/// </summary>
		public AffixUtility()
		{
		}

		/// <summary>
		///     Adds a prefix to a word
		/// </summary>
		/// <param name="word" type="string">
		///     <para>
		///         The word to add the prefix to
		///     </para>
		/// </param>
		/// <param name="rule" type="NetSpell.SpellChecker.Dictionary.Affix.AffixRule">
		///     <para>
		///         The AffixRule to use when adding the prefix
		///     </para>
		/// </param>
		/// <returns>
		///     The word with the prefix added
		/// </returns>
		public static string AddPrefix(string word, AffixRule rule)
		{
			foreach (AffixEntry entry in rule.AffixEntries)
			{
				// check that this entry is valid
				if (word.Length >= entry.ConditionCount)
				{
					int passCount = 0;
					for (int i = 0;  i < entry.ConditionCount; i++) 
					{
						int charCode = (int)word[i];
						if ((entry.Condition[charCode] & (1 << i)) == (1 << i))
						{
							passCount++;
						}
						else 
						{
							break;
						}
					}
					if (passCount == entry.ConditionCount)
					{
						string tempWord = word.Substring(entry.StripCharacters.Length);
						tempWord = entry.AddCharacters + tempWord;
						return tempWord;
					}
				}
			}
			return word;
		}

		/// <summary>
		///     Adds a suffix to a word
		/// </summary>
		/// <param name="word" type="string">
		///     <para>
		///         The word to get the suffix added to
		///     </para>
		/// </param>
		/// <param name="rule" type="NetSpell.SpellChecker.Dictionary.Affix.AffixRule">
		///     <para>
		///         The AffixRule to use when adding the suffix
		///     </para>
		/// </param>
		/// <returns>
		///     The word with the suffix added
		/// </returns>
		public static string AddSuffix(string word, AffixRule rule)
		{
			foreach (AffixEntry entry in rule.AffixEntries)
			{
				// check that this entry is valid
				if (word.Length >= entry.ConditionCount)
				{
					int passCount = 0;
					for (int i = 0;  i < entry.ConditionCount; i++) 
					{
						int charCode = (int)word[word.Length - (entry.ConditionCount - i)];
						if ((entry.Condition[charCode] & (1 << i)) == (1 << i))
						{
							passCount++;
						}
						else 
						{
							break;
						}
					}
					if (passCount == entry.ConditionCount)
					{
						int tempLen = word.Length - entry.StripCharacters.Length;
						string tempWord = word.Substring(0, tempLen);
						tempWord += entry.AddCharacters;
						return tempWord;
					}
				}
			}
			return word;
		}

		/// <summary>
		///     Generates the condition character array
		/// </summary>
		/// <param name="conditionText" type="string">
		///     <para>
		///         the text form of the conditions
		///     </para>
		/// </param>
		/// <param name="entry" type="NetSpell.SpellChecker.Dictionary.Affix.AffixEntry">
		///     <para>
		///         The AffixEntry to add the condition array to
		///     </para>
		/// </param>
		public static void EncodeConditions(string conditionText, AffixEntry entry)
		{
			// clear the conditions array
			for (int i=0; i < entry.Condition.Length; i++)
			{
				entry.Condition[i] = 0;
			}

			// if no condition just return
			if (conditionText == ".") 
			{
				entry.ConditionCount = 0;
				return;
			}

			bool neg = false;  /* complement indicator */
			bool group = false;  /* group indicator */
			bool end = false;   /* end condition indicator */
			int num = 0;    /* number of conditions */
			
			char [] memberChars = new char[200];
			int numMember = 0;   /* number of member in group */

			foreach (char cond in conditionText)
			{
				// parse member group
				if (cond == '[')
				{
					group = true;  // start a group
				}
				else if (cond == '^' && group)
				{
					neg = true; // negative group
				}
				else if (cond == ']')
				{
					end = true; // end of a group
				}
				else if (group)
				{
					// add chars to group
					memberChars[numMember] = cond;
					numMember++;
				}
				else
				{
					end = true;  // no group
				}

				// set condition
				if (end)
				{
					if (group)
					{
						if (neg)
						{
							// turn all chars on
							for (int j=0; j < entry.Condition.Length; j++) 
							{
								entry.Condition[j] = entry.Condition[j] | (1 << num);
							}
							// turn off chars in member group
							for (int j=0; j < numMember; j++) 
							{
								int charCode = (int)memberChars[j];
								entry.Condition[charCode] = entry.Condition[charCode] & ~(1 << num);
							}
						}
						else 
						{
							// turn on chars in member group
							for (int j=0; j < numMember; j++) 
							{
								int charCode = (int)memberChars[j];
								entry.Condition[charCode] = entry.Condition[charCode] | (1 << num);
							}
						}
						group = false;
						neg = false;
						numMember = 0;
					} // if group
					else
					{
						if (cond == '.')
						{
							// wild card character, turn all chars on
							for (int j=0; j < entry.Condition.Length; j++) 
							{
								entry.Condition[j] = entry.Condition[j] | (1 << num);
							}
						}
						else 
						{
							// turn on char
							int charCode = (int)cond;
							entry.Condition[charCode] = entry.Condition[charCode] | (1 << num);
						}
					} // not group

					end = false;
					num++;
				} // if end
			} // foreach char

			entry.ConditionCount = num;
			return;

		}

		/// <summary>
		///     Removes the affix prefix rule entry for the word if valid
		/// </summary>
		/// <param name="word" type="string">
		///     <para>
		///         The word to be modified
		///     </para>
		/// </param>
		/// <param name="entry" type="NetSpell.SpellChecker.Dictionary.Affix.AffixEntry">
		///     <para>
		///         The affix rule entry to use
		///     </para>
		/// </param>
		/// <returns>
		///     The word after affix removed.  Will be the same word if affix could not be removed.
		/// </returns>
		/// <remarks>
		///		This method does not verify that the returned word is a valid word, only that the affix can be removed
		/// </remarks>
		public static string RemovePrefix(string word, AffixEntry entry)
		{

			int tempLength = word.Length - entry.AddCharacters.Length;
			if ((tempLength > 0)  
				&& (tempLength + entry.StripCharacters.Length >= entry.ConditionCount) 
				&& (word.StartsWith(entry.AddCharacters)))
			{
				// word with out affix
				string tempWord = word.Substring(entry.AddCharacters.Length);
				// add back strip chars
				tempWord = entry.StripCharacters + tempWord;
				// check that this is valid
				int passCount = 0;
				for (int i = 0;  i < entry.ConditionCount; i++) 
				{
					int charCode = (int)tempWord[i];
					if ((entry.Condition[charCode] & (1 << i)) == (1 << i))
					{
						passCount++;
					}
				}
				if (passCount == entry.ConditionCount)
				{
					return tempWord;
				}
				
			}
			return word;
		}
		/// <summary>
		///     Removes the affix suffix rule entry for the word if valid
		/// </summary>
		/// <param name="word" type="string">
		///     <para>
		///         The word to be modified
		///     </para>
		/// </param>
		/// <param name="entry" type="NetSpell.SpellChecker.Dictionary.Affix.AffixEntry">
		///     <para>
		///         The affix rule entry to use
		///     </para>
		/// </param>
		/// <returns>
		///     The word after affix removed.  Will be the same word if affix could not be removed.
		/// </returns>
		/// <remarks>
		///		This method does not verify that the returned word is a valid word, only that the affix can be removed
		/// </remarks>
		public static string RemoveSuffix(string word, AffixEntry entry)
		{
			int tempLength = word.Length - entry.AddCharacters.Length;
			if ((tempLength > 0)  
				&&  (tempLength + entry.StripCharacters.Length >= entry.ConditionCount)
				&& (word.EndsWith(entry.AddCharacters)))
			{
				// word with out affix
				string tempWord = word.Substring(0, tempLength);
				// add back strip chars
				tempWord += entry.StripCharacters;
				// check that this is valid
				int passCount = 0;
				for (int i = 0;  i < entry.ConditionCount; i++) 
				{
					int charCode = (int)tempWord[tempWord.Length - (entry.ConditionCount - i)];
					if ((entry.Condition[charCode] & (1 << i)) == (1 << i))
					{
						passCount++;
					}
				}
				if (passCount == entry.ConditionCount)
				{
					return tempWord;
				}
			}
			return word;
		}
	}
}
